Recently, a method for forming carbon nanotubes (CNTs) within a via between multilayer interconnects of a semiconductor device has been proposed with a view to reducing interconnect resistance. Because of their quantization conductivity, CNTs offer the possibility of forming low-resistance interconnects in an LSI and so replacing metal interconnects. Further, since the structure of a CNT is tubular, and vertical deposition by the CVD method is possible, this technique is excellently compatible with the conventional vertical interconnect formation process of a device.
As described above, a CNT is a new material which is expected to have excellent electrical properties in vertically arranged interconnects. With such CNTs, it is possible to realize low-resistance interconnects, particularly when the distance between interconnects is great. On the other hand, to apply CNTs to contacts, a measure for increasing their mean free path is important. For example, the measure which can be taken is doping the CNTs with an element such as boron (Br) or nitrogen (N) and so increasing the carriers transported.